Communication device and integrated circuit

ABSTRACT

Provided is a radio communication base station device which can suppress a use amount of an SRS communication resource. In this device, a correlation rule setting unit ( 102 ) sets a rule for correlating a preamble with an SRS transmission time interval so that the preamble transmission time band and the SRS transmission time band are in the same transmission time band. An SRS transmission band decision unit ( 103 ) decides a time interval of a transmission time band which can transmit the SRS according to the preamble transmission time interval inputted from a preamble transmission band decision unit ( 101 ) and the correlation rule setting unit ( 102 ).

TECHNICAL FIELD

The present disclosure relates to a radio communication base stationapparatus and an association setting method.

BACKGROUND ART

The 3GPP RAN LTE (Long Term Evolution) is currently studyingtransmission of SRSs (Sounding Reference Signals) for channel qualityestimation (CQI (Channel Quality Indicator) estimation) for frequencyscheduling, reception timing detection and transmission power control onuplink from a radio communication mobile station apparatus (hereinafterabbreviated as a “mobile station”) to a radio communication base stationapparatus (hereinafter abbreviated as a “base station”) (e.g. seeNon-Patent Document 1).

According to the 3GPP RAN LTE, for example, an SRS is formed with one LB(Long Block) and the time length of the SRS is 71.4 μs including the CP(Cyclic Prefix) and the reference signal. Furthermore, the mobilestation transmits SRSs periodically (e.g. at 1-subframe intervals=at 1ms intervals), according to command from the base station. Furthermore,a plurality of bandwidths, such as 1.25 MHz, 5 MHz and 10 MHz, areprovided for the SRS transmission bandwidth, and a bandwidthcorresponding to the propagation condition of the mobile station is set.For example, a mobile station located at a cell edge where thepropagation condition is poor and transmission power is limited does nothave power necessary to transmit a wideband SRS, and so the mobilestation transmits a narrowband (e.g. 1.25 MHz) SRS. When such anarrowband SRS is used, wideband CQI estimation is performed over aplurality of transmission time fields by performing frequency hopping.

Furthermore, the 3GPP RAN LTE is studying the use of random accesspreamble (hereinafter abbreviated as a “preamble”) for initial access ofa mobile station, updating of transmission timing and CQI estimation onuplink from a mobile station to a base station (e.g. see Non-PatentDocument 2). A preamble is a signal including identification informationabout a mobile station, and each mobile station randomly selects one ofa plurality of code sequences set up in advance by a base station orselects one code sequence according to command from the base station.Each mobile station then transmits a preamble generated based on theselected code sequence to the base station. According to the 3GPP RANLTE, the preamble is formed with one subframe, for example, and the timelength of the preamble is 1 ms (=14 LBs) including the CP, the preambleand the guard time, which is a non-transmission period. Furthermore, themobile station transmits preambles periodically (e.g. at 10-subframeintervals=10 ms intervals), according to command from the base stationas in the case of SRS. Furthermore, for the preamble transmissionbandwidth, for example, 1.08 MHz is set (=6 RBs (Resource Blocks)).Furthermore, when the preamble is transmitted, frequency hopping isperformed to provide frequency diversity gain and improve the preambledetection performance as in the case of the SRS.

Furthermore, a preamble transmitted from a mobile station which has notestablished synchronization with a base station on uplink entails adelay matching the round trip propagation delay time (RTD) at receptiontiming at the time of reception in the base station. Therefore, a guardtime is set in the preamble as described above to prevent the preamblefrom delaying and causing interference with the signal of the nextsubframe.

When transmitting an SRS, resources of the time domain and frequencydomain may be assigned thereto exclusive of other signals (e.g. seeNon-Patent Document 3). Here, an SRS is assigned to the first 1 LB inone subframe (=1 ms) of PUSCH (Physical Uplink Shared Channel), which isformed with 14 LBs and assigned transmission data of the mobile station,and transmitted to the base station.

-   Non-Patent Document 1: NTT DoCoMo, Fujitsu, Mitsubishi Electric,    NEC, Panasonic, Sharp, Toshiba Corporation, R1-072938, “Necessity of    Multiple Bandwidths for Sounding Reference Signals”, 3GPP TSG RAN    WG1 Meeting #49bis, Orlando, USA, Jun. 25-29, 2007-   Non-Patent Document 2: Texas Instruments, R1-063213, “Improved    Non-Synchronized Random Access structure for E-UTRA”, 3GPP TSG RAN    WG1 Meeting #47bis, Riga, Latvia, Nov. 6-10, 2006-   Non-Patent Document 3: NEC Group, NTT DoCoMo, R1-072824, “Discussion    on Uplink Reference Signal”, 3GPP TSG RAN WG1 Meeting #49bis,    Orlando, USA, 25-29 Jun. 2007

BRIEF SUMMARY

However, with the above-described conventional technique of performingtransmission by assigning the SRS to the first LB in a subframe, thefirst LB in a subframe is more frequently used to transmit the SRS asthe number of mobile stations in a cell increases. That is, theproportion of communication resources used to transmit SRSs increases asthe number of mobile stations in the cell increases. Therefore,according to the above-described conventional technique, when the numberof mobile stations within the cell increases, communication resourcesavailable for data transmission decrease, and, as a result, the datatransmission efficiency is reduced.

An embodiment provides a radio communication base station apparatus andan association setting method capable of suppressing the amount ofcommunication resources used for SRSs.

In an embodiment, a radio communication base station apparatus adopts aconfiguration including a receiving section that receives a first signalwhich is provide with a guard time and which is transmittedperiodically, and a second signal which is transmitted periodically, asetting section that sets an association between the first signal andthe second signal such that a first transmission field for the firstsignal matches a second transmission field for the second signal, and adetermining section that determines the second transmission field basedon the first transmission field and the association.

In an embodiment, the amount of communication resources used for SRSsmay be reduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of a base stationaccording to an embodiment;

FIG. 2 is a block diagram illustrating a configuration of a mobilestation that transmits a preamble according to an embodiment;

FIG. 3 is a block diagram illustrating a configuration of a mobilestation that transmits an SRS according to an embodiment;

FIG. 4 is a diagram illustrating an association of a transmission timefield according to an embodiment;

FIG. 5 is a diagram illustrating a preamble transmission time fieldaccording to an embodiment;

FIG. 6 is an operation sequence of a mobile communication systemaccording to an embodiment;

FIG. 7 is a diagram illustrating a preamble transmission time fieldaccording to an embodiment;

FIG. 8 is a block diagram illustrating a configuration of a base stationaccording to an embodiment;

FIG. 9 is a diagram illustrating an association of a transmission timefield according to an embodiment;

FIG. 10 is a diagram illustrating another association of a transmissiontime field of an embodiment (first example of association); and

FIG. 11 is a diagram illustrating a further association of atransmission time field of an embodiment (second example ofassociation).

DETAILED DESCRIPTION

Hereinafter, example embodiments will be explained in detail withreference to the accompanying drawings.

Embodiment 1

FIG. 1 shows a configuration of base station 100 according to thepresent embodiment. Base station 100 receives a preamble from mobilestation 200 (FIG. 2) which will be described later and receives an SRSfrom mobile station 300 (FIG. 3) which will be described later.

Preamble transmission field determining section 101 determines the timeinterval of the transmission time field (subframe) in which the mobilestation can transmit a preamble. Preamble transmission field determiningsection 101 then outputs the determined preamble transmission timeinterval to SRS transmission field determining section 103, controlsignal generation section 104 and time field identifying section 109.

Association rule setting section 102 sets rules for associating thetransmission time intervals for the preamble and SRS. Association rulesetting section 102 then outputs the association rules set, to SRStransmission field determining section 103. Details of the setting ofthe association rules in association rule setting section 102 will bedescribed later.

SRS transmission field determining section 103 determines the timeinterval of the transmission time field (subframe) in which the SRS canbe transmitted, based on the preamble transmission time intervalinputted from preamble transmission field determining section 101 andthe association rules inputted from association rule setting section102. SRS transmission field determining section 103 then outputs thedetermined SRS transmission time interval to control signal generationsection 104 and time field identifying section 109. Details of theprocessing of determining the SRS transmission time field in SRStransmission field determining section 103 will be described later.

Control signal generation section 104 generates a control signalincluding the preamble transmission time interval inputted from preambletransmission field determining section 101 and the SRS transmission timeinterval inputted from SRS transmission field determining section 103.Control signal generation section 104 then outputs the control signalgenerated to modulation section 105.

Modulation section 105 modulates the control signal inputted fromcontrol signal generation section 104 and outputs the modulated controlsignal to radio transmitting section 106.

Radio transmitting section 106 performs radio processing such as D/Aconversion, up-conversion on the control signal and transmits thecontrol signal to mobile station 200 and mobile station 300 via antenna107.

On the other hand, radio receiving section 108 receives a signaltransmitted from mobile station 200 and mobile station 300 via antenna107, performs radio processing such as down-conversion, A/D conversionon the received signal and outputs the received signal to time fieldidentifying section 109.

Time field identifying section 109 identifies the preamble transmissiontime field (subframe) and the SRS transmission time field (subframe)based on the preamble transmission time interval inputted from preambletransmission field determining section 101 and the SRS transmission timeinterval inputted from SRS transmission field determining section 103,outputs the received preamble to demodulation section 110 and thereceived SRS to demodulation section 112.

Demodulation section 110 demodulates the preamble inputted from timefield identifying section 109 and outputs the demodulated preamble topreamble detection section 111.

Preamble detection section 111 determines the correlation between theknown preamble code sequence set up in advance in the system and thepreamble inputted from demodulation section 110, and detects thepreamble. Preamble detection section 111 then outputs a preambledetection result indicating the detected preamble.

Demodulation section 112 demodulates the SRS inputted from time fieldidentifying section 109 and outputs the demodulated SRS to CQIestimation section 113.

CQI estimation section 113 performs CQI estimation based on the SRSinputted from demodulation section 112. CQI estimation section 113 thenoutputs the estimated CQI estimate value.

Next, FIG. 2 shows a configuration of mobile station 200 according tothe present embodiment. Mobile station 200 transmits a preamble to basestation 100 (FIG. 1).

Radio receiving section 202 receives a control signal transmitted frombase station 100 via antenna 201, performs radio processing such asdown-conversion, A/D conversion on the control signal and outputs thecontrol signal to demodulation section 203.

Demodulation section 203 demodulates the control signal and outputs thedemodulated control signal to transmission time interval detectionsection 204.

Transmission time interval detection section 204 detects the preambletransmission time interval included in the control signal inputted fromdemodulation section 203 and outputs the detected preamble transmissiontime interval to preamble generation section 205.

Preamble generation section 205 randomly selects one preamble codesequence from known preamble code sequences set up in advance in thesystem in the preamble transmission time field (subframe) obtained basedon the preamble transmission time interval inputted from transmissiontime interval detection section 204. Preamble generation section 205then generates a preamble based on the selected code sequence. Preamblegeneration section 205 then outputs the preamble generated to guard timeadding section 206.

Guard time adding section 206 adds a guard time of a predetermined timelength to the preamble inputted from preamble generation section 205.Guard time adding section 206 then outputs the preamble with a guardtime to modulation section 207.

Modulation section 207 modulates the preamble and outputs the modulatedpreamble to radio transmitting section 208.

Radio transmitting section 208 performs radio processing such as D/Aconversion, up-conversion on the preamble inputted from modulationsection 207 and transmits the preamble to base station 100 via antenna201.

Next, FIG. 3 shows a configuration of mobile station 300 according tothe present embodiment. Mobile station 300 transmits the SRS to basestation 100 (FIG. 1).

Radio receiving section 302 receives a control signal transmitted frombase station 100 via antenna 301, performs radio processing such asdown-conversion and A/D conversion on the control signal, and outputsthe control signal to demodulation section 303.

Demodulation section 303 demodulates the control signal and outputs thedemodulated control signal to transmission time interval detectionsection 304.

Transmission time interval detection section 304 detects the SRStransmission time interval included in the control signal inputted fromdemodulation section 303, and outputs the detected SRS transmission timeinterval to SRS generation section 305.

SRS generation section 305 generates a known SRS code sequence commandedfrom base station 100 in advance, in the SRS transmission time field(subframe) obtained based on the SRS transmission time interval inputtedfrom transmission time interval detection section 304. SRS generationsection 305 then outputs the generated SRS to arrangement section 307.

Preamble transmission field information setting section 306 sets thepositions and time lengths of the CP, preamble and guard time in thepreamble transmission time field. Preamble transmission fieldinformation setting section 306 then outputs preamble transmission fieldinformation indicating the positions and time lengths of the CP,preamble and guard time in the preamble transmission time field, toarrangement section 307.

Arrangement section 307 arranges the SRS in the preamble transmissiontime field (subframe) based on the preamble transmission fieldinformation inputted from preamble transmission field informationsetting section 306. To be more specific, arrangement section 307arranges the SRS in the guard time position in the preamble. Forexample, arrangement section 307 arranges the SRS in the guard timeposition in the preamble such that the time interval between thepreamble and the SRS becomes maximum. Arrangement section 307 outputsthe arranged SRS to modulation section 308. Details of the SRSarrangement processing in arrangement section 307 will be describedlater.

Modulation section 308 modulates the SRS and outputs the modulated SRSto radio transmitting section 309.

Radio transmitting section 309 performs radio processing such as D/Aconversion, up-conversion on the SRS inputted from modulation section308 and transmits the SRS to base station 100 via antenna 301.

Next, details of the setting of the association rules by associationrule setting section 102 of base station 100 (FIG. 1), the processing ofdetermining the SRS transmission time interval in SRS transmission fielddetermining section 103 and the processing of SRS arrangement inarrangement section 307 of mobile station 300 (FIG. 3) will beexplained.

To be more specific, association rule setting section 102 sets rulesaccording to following equation 1.m×(preamble transmission time interval)=n×(SRS transmission timeinterval)  (Equation 1)

where m and n are positive integers. That is, association rule settingsection 102 sets m and n. By this means, the preamble transmission timefield and the SRS transmission time field match in a transmission timefield that satisfies equation 1. That is, the preamble and the SRS usethe same transmission time field.

Next, SRS transmission field determining section 103 determines theinterval of the SRS transmission time field according to the preambletransmission time interval inputted from preamble transmission fielddetermining section 101 and the rules (m and n) set in association rulesetting section 102. That is, SRS transmission field determining section103 determines the SRS transmission time interval from (m/n)×(preambletransmission time interval) based on equation 1.

This will be explained more specifically below. Here, assuming that thepreamble transmission time interval determined in preamble transmissionfield determining section 101 is 10 subframes, association rule settingsection 102 sets m=1 and n=2. Furthermore, suppose the system bandwidthis 24 RBs, the bandwidth for arranging the preamble is 6 RBs and thebandwidth for arranging the SRS is 24 RBs. Furthermore, suppose the timelength of the preamble is 1 subframe, and 1 subframe is 14 LBs.Furthermore, suppose the time length of the SRS is 1 LB.

By this means, SRS transmission field determining section 103 determinesthe SRS transmission time interval to be 5 subframes from (½)×(10subframes).

Thus, as shown in FIG. 4, while the time interval of the preambletransmission time field is 10 subframes, the time interval of the SRStransmission time field is 5 subframes. Furthermore, the transmissiontime field of the preamble, which requires a longer transmission timeinterval than the SRS, constantly matches the SRS transmission timefield. That is, since part of the SRS transmission time field (half ofthe whole in FIG. 4) is transmitted using the same transmission timefield as the preamble transmission time field, communication resourcesused for the SRS can be reduced.

When one of m and n is 1 in the above equation, the preambletransmission time field constantly matches the SRS transmission timefield in the transmission time field for one of the preamble and the SRShaving the longer time interval of the transmission time field. On theother hand, when m=n=1, the preamble transmission time field constantlymatches the SRS transmission time field, and, consequently, the preambletransmission time field is the only communication resource used for theSRS.

On the other hand, arrangement section 307 of mobile station 300 (FIG.3) arranges the generated SRS in the position of the guard time in thepreamble transmission time field such that the time interval between thepreamble and the SRS becomes maximum.

To be more specific, arrangement section 307 arranges the SRS in theguard time of one subframe including the CP, the preamble and the guardtime, as shown in FIG. 5. Here, arrangement section 307 arranges the SRSat the tail end of the subframe such that the time interval between thepreamble and the SRS becomes maximum as shown in FIG. 5.

Here, the preamble and the SRS shown in FIG. 5 are transmitted fromdifferent mobile stations, mobile station 200 (FIG. 2) and mobilestation 300 (FIG. 3). Furthermore, uplink synchronization is establishedbetween mobile station 300 that transmits the SRS and base station 100,whereas uplink synchronization is not established between mobile station200 that transmits the preamble and base station 100. That is, sincemobile station 300 transmits the SRS taking into account the RTD betweenmobile station 300 and base station 100, the SRS reception timing inbase station 100 is not delayed. On the other hand, since mobile station200 transmits the preamble without taking into account the RTD, thepreamble reception timing in base station 100 is delayed by the RTD.

However, since arrangement section 307 of mobile station 300 arrangesthe SRS at the tail end of the subframe such that the time intervalbetween the preamble and the SRS becomes maximum, even if the preamblereception timing shown in FIG. 5 delays into the guard time, basestation 100 can reduce interference between the preamble and the SRS.Especially when the RTD satisfies following equation 2, no interferenceoccurs between the preamble and the SRS.RTD≦GT−(CP+SRS)  (Equation 2)

where GT is the time length of the guard time of the preambletransmission time field (subframe), CP is the CP time length of the SRS(value corresponding to delay spread) and SRS is the time length of theSRS.

When, for example, the values determined in the 3GPP RAN LTE are appliedto equation 2, RTD≦26 μs. Here, suppose GT=97.4 μs, CP=4.8 μs andSRS=66.6 μs. Furthermore, the RTD increases by 6.67 μs every time thedistance between base station 100 and mobile station 200 increases by 1km. That is, when the distance between base station 100 and mobilestation 200 is equal to or less than approximately 3.9 (=26/6.67) km, nointerference occurs between the preamble and the SRS shown in FIG. 5.

Next, operation of a mobile communication system formed with basestation 100, mobile station 200 and mobile station 300 will beexplained. FIG. 6 shows an operation sequence of the mobilecommunication system according to the present embodiment.

In ST 101 (step), preamble transmission field determining section 101 ofbase station 100 determines the preamble transmission time interval(e.g. 10 subframes shown in FIG. 4) first and SRS transmission fielddetermining section 103 determines the SRS transmission time interval(e.g. 5 subframes shown in FIG. 4). Base station 100 then transmits thepreamble transmission time interval and the SRS transmission timeinterval to mobile station 200 and mobile station 300 respectively.

In ST 102, in mobile station 200 having received the preambletransmission time interval and SRS transmission time interval,transmission time interval detection section 204 detects the preambletransmission time interval, and preamble generation section 205calculates the preamble transmission time field and generates apreamble. Mobile station 200 then transmits the preamble to base station100.

Similarly in ST 103, in mobile station 300 having received the preambletransmission time interval and the SRS transmission time interval,transmission time interval detection section 304 detects the SRStransmission time interval, and SRS generation section 305 calculatesthe SRS transmission time field and generates an SRS. Furthermore,arrangement section 307 arranges the SRS in the position of the guardtime in the preamble transmission time field. Mobile station 300 thentransmits the SRS to base station 100.

Next, in ST 104, base station 100 receives the preamble from mobilestation 200 and the SRS from mobile station 300 according to thepreamble transmission time interval and the SRS transmission timeinterval reported to mobile station 200 and mobile station 300.

Here, assuming that the SRS transmission time interval (transmissiontime interval T shown in FIG. 6) is 5 subframes and the preambletransmission time interval (transmission time interval 2T shown in FIG.6) is 10 subframes, the relational equation of equation 1 abovesatisfies (preamble transmission time interval)=2×(SRS transmission timeinterval). That is, while the base station receives a preamble frommobile station 200 one time, the base station receives an SRS frommobile station 300 twice. Furthermore, the preamble transmission timefield from mobile station 200 constantly matches the SRS transmissiontime field from mobile station 300. To be more specific, in transmissiontime interval T (5 subframes) after base station 100 receives thepreamble from mobile station 200 and the SRS from mobile station 300 inST 104, base station 100 receives only the SRS from mobile station 300in ST 105. Furthermore, in further transmission time interval T (5subframes) after ST 105, that is, in transmission time interval 2T (10subframes) after ST 104, base station 100 receives the preamble frommobile station 200 and SRS from mobile station 300 in ST 106.

Thus, in the preamble transmission time field, not only the preamble butalso the SRS is received constantly, and therefore it is possible toreduce the communication resources to be secured for the SRStransmission time field.

Thus, according to the present embodiment, the SRS transmission timeinterval is associated with the preamble transmission time interval.This allows the SRS transmission time field to match the preambletransmission time field, and therefore it is possible to suppress theamount of communication resources used to transmit the SRS. Furthermore,when the SRS is arranged in the preamble transmission time field, theSRS may be arranged in the guard time such that the time intervalbetween the preamble and the SRS becomes maximum, and, therefore, evenwhen the preamble reception timing is delayed, it is possible tominimize interference between the preamble and the SRS.

A case has been described with the present embodiment where the preambletransmission bandwidth (24 RBs) is different from the SRS transmissionbandwidth (6 RBs) as shown in FIG. 4, but the preamble transmissionbandwidth may be equal to the SRS transmission bandwidth.

Furthermore, a case has been described with the present embodiment wherethe base station transmits a control signal including an SRStransmission time interval to each mobile station, but it is notnecessarily to report the SRS transmission time interval in a controlsignal to each mobile station. For example, instead of reporting the SRStransmission time interval in a control signal to each mobile station,the base station may report the association rules to each mobilestation. By this means, each mobile station can calculate the SRStransmission time interval based on the preamble transmission timeinterval and the association rules. Furthermore, according to thepresent embodiment, the entire system may set in advance the associationrules. Thus, the base station needs to report only the preambletransmission time interval to each mobile station, and therefore canreduce the amount of information for reporting the SRS transmission timeinterval and the association rules.

Furthermore, a case has been described with the present embodiment wherepreamble generation section 205 of mobile station 200 (FIG. 2) generatesa preamble based on a preamble code sequence selected randomly frompreamble code sequences set up in advance by the system. However,preamble generation section 205 may also generate a preamble based on apreamble code sequence given from base station 100 (FIG. 1). Thus, basestation 100 indicates the preamble code sequence to mobile station 200,so that the preamble of mobile station 200 does not collide with thepreambles of other mobile stations, and therefore it is possible toprevent collision between the preambles based on the same preamble codesequence.

Furthermore, modulation section 105 (FIG. 1) of base station 100 of thepresent embodiment, modulation section 207 (FIG. 2) of mobile station200 and modulation section 308 (FIG. 3) of mobile station 300 mayperform DFT (Discrete Fourier Transform) processing, transmission bandmapping processing and IFFT (Inverse Fast Fourier Transform) processing.Here, the DFT processing transforms the signal from a time domain signalto a frequency domain signal. Furthermore, the transmission band mappingprocessing arranges the signal transformed to a frequency domain signalthrough the DFT processing in a predetermined transmission band.Furthermore, the IFFT processing applies IFFT to the signal subjected tothe transmission band mapping processing to transform the signal from afrequency domain signal to a time domain signal.

Likewise, demodulation section 110 and demodulation section 112 of basestation 100, demodulation section 203 of mobile station 200 anddemodulation section 303 of mobile station 300 may perform FFT (FastFourier Transform) processing, transmission band demapping processingand IDFT (Inverse Discrete Fourier Transform) processing. Here, the FFTprocessing applies FFT to the received signal to transform the signalfrom a time domain signal to a frequency domain signal. Furthermore, thetransmission band demapping processing extracts a predeterminedtransmission band including the transmitted signal from the signaltransformed to the frequency domain. Furthermore, the IDFT processingapplies IDFT processing to the signal subjected to the transmission banddemapping processing to transform the signal from a frequency domainsignal to a time domain signal.

Embodiment 2

In the present embodiment, an SRS is arranged at the beginning of apreamble transmission time field.

Guard time adding section 206 (FIG. 2) of mobile station 200 accordingto the present embodiment adds a guard time of the same time length asthe SRS length before the preamble inputted from preamble generationsection 205 and also adds a guard time of a time length corresponding to(1 subframe length—preamble length—SRS length) after the preamble.

On the other hand, when arranging an SRS in a preamble transmission timefield (subframe), arrangement section 307 (FIG. 3) of mobile station 300according to the present embodiment arranges the SRS at the beginning ofthe preamble transmission time field (subframe).

This will be explained more specifically below. Here, suppose thepreamble transmission time field is formed with 14 LBs and the timelength of the SRS is 1 LB as with Embodiment 1.

Therefore, as shown in FIG. 7, arrangement section 307 arranges thegenerated SRS at the beginning of the preamble transmission time field(subframe). On the other hand, mobile station 200 arranges the CP andthe preamble directly after the position where the SRS is arranged. Thatis, as shown in FIG. 7, in mobile station 200, the CP and preamble arearranged in that order from the position 1 LB (i.e. the SRS length) fromthe beginning of the preamble transmission time field (subframe).Furthermore, as shown in FIG. 7, in 1 subframe, the rest of thetransmission time field other than the transmission time field where theSRS and preamble (including the CP) are arranged, constitutes the guardtime.

As described above, by this means, the SRS from mobile station 300 doesnot delay in base station 100. Therefore, even when base station 100receives a signal with no interval between the SRS and the preamble asshown in FIG. 7, the SRS never slips into the rear part where thepreamble is arranged, and therefore the SRS and the preamble do notinterfere with each other in the same transmission time field. On theother hand, in base station 100, the preamble is delayed by the RTD.However, as shown in FIG. 7, the present embodiment eliminates theinterval between the SRS and the preamble and secures a maximal guardtime after the preamble. Therefore, when the RTD satisfies equation 1,base station 100 can prevent interference between the preamble and thesignal of the next transmission time field (subframe) as in the case ofEmbodiment 1.

Thus, according to the present embodiment, the SRS is arranged at thebeginning of the preamble transmission time field. This makes itpossible to provide similar effects to Embodiment 1 and preventinterference between the SRS and the preamble completely.

Embodiment 3

A case has been described with Embodiment 1 where the preamble and SRStransmission time fields are made to match each other, but a case willbe explained now with the present embodiment where the preamble and SRStransmission time fields and the transmission band are made to matcheach other.

This will be explained more specifically below. In the followingexplanations, suppose that preambles and SRSs are transmitted usingfrequency hopping.

FIG. 8 shows a configuration of base station 400 according to thepresent embodiment. In FIG. 8, the same components as those inEmbodiment 1 (FIG. 1) will be assigned the same reference numerals, andexplanations thereof will be omitted.

Preamble transmission field determining section 401 of base station 400according to the present embodiment determines a time interval(subframe) in which each mobile station can transmit the preamble and atransmission band in which the preamble can be transmitted.

Association rule setting section 402 sets a rule for associating thepreamble and SRS transmission time intervals with their transmissionbands. Details of the setting of association rules in association rulesetting section 402 will be described later.

SRS transmission field determining section 403 determines a timeinterval (subframe) in which the SRS can be transmitted and atransmission band in which the SRS can be transmitted, based on thepreamble transmission time interval and the preamble transmission bandinputted from preamble transmission field determining section 401 andthe association rules inputted from association rule setting section402.

Control signal generation section 404 generates a control signalincluding the preamble transmission time interval and the preambletransmission band inputted from preamble transmission field determiningsection 401 and the SRS transmission time interval and the SRStransmission band inputted from SRS transmission field determiningsection 403.

On the other hand, time domain/frequency domain identifying section 405identifies the transmission time field and the transmission band of thepreamble and the SRS based on the preamble transmission time intervaland the preamble transmission band inputted from preamble transmissionfield determining section 401 and the SRS transmission time interval andthe SRS transmission band inputted from SRS transmission fielddetermining section 403, outputs the received preamble to demodulationsection 110 and the received SRS to demodulation section 112.

Next, the details of the association rule setting in association rulesetting section 402 of base station 400 (FIG. 8) and the processing ofdetermining the SRS transmission field in SRS transmission fielddetermining section 403, will be explained.

Here, the preamble transmission time interval determined in preambletransmission field determining section 401 is assumed to be 5 subframesand association rule setting section 402 sets m=1 and n=5. Moreover,suppose the system bandwidth is 24 RBs, the preamble transmissionbandwidth is 6 RBs and the SRS transmission bandwidth is 6 RBs.Furthermore, different mobile stations transmit SRS 1 and SRS 2respectively. Furthermore, both the preamble and the SRS are subjectedto frequency hopping whereby the transmission band is changed pertransmission time field.

As shown in FIG. 9, association rule setting section 402 setsassociation rules such that the preamble transmission band matches theSRS transmission band in a transmission time field that satisfies1×(preamble transmission time interval)=5×(SRS transmission timeinterval).

Since the preamble transmission time interval inputted from preambletransmission field determining section 401 is 5 subframes, SRStransmission field determining section 403 determines the SRStransmission time interval to be 1 subframe from (m/n)×(preambletransmission time interval), based on equation 1. Furthermore, SRStransmission field determining section 403 determines the transmissionband in which the SRS transmission band and the preamble transmissionband match, in a transmission time field that satisfies equation 1.

That is, as shown in FIG. 9, the SRS is included in part of the preamblein the preamble transmission time field. By this means, the preambletransmission band can include the preamble and SRS in the preambletransmission time field, and therefore it is possible to assign theremaining transmission band, for example, to PUSCH, for datatransmission.

Thus, according to the present embodiment, when a preamble and SRS aresubjected to frequency hopping, the preamble transmission band and theSRS transmission band are made to match each other. This makes itpossible to maintain a frequency diversity effect through frequencyhopping and transmit an SRS in the same transmission time field and thesame transmission band as those for a preamble. Therefore, the presentembodiment can reduce the communication resources used for SRSs.

A case has been described with the present embodiment where the SRStransmission band is determined such that the SRS frequency hoppingpattern matches the preamble frequency hopping pattern in a transmissiontime field in which the preamble and the SRS match each other. However,according to the present disclosure, the preamble transmission band maybe determined so that the preamble frequency hopping pattern matches theSRS frequency hopping pattern.

Furthermore, a case has been described with the present embodiment wherethere is one SRS in the transmission time field in which the preambleand the SRS match each other, but the present disclosure is alsoapplicable to a case where there are a plurality of SRSs in thetransmission time field in which the preamble and the SRS match eachother. For example, as shown in FIG. 10, when SRS 1 and SRS 2 arearranged in different transmission bands in the same transmission timefield, a transmission band that matches that of the preamble may begiven to SRS 1 and SRS 2 evenly. To be more specific, as shown in FIG.10, in the preamble transmission time field, both transmission bands ofSRS 1 and SRS 2 are made to match two different preamble transmissionbands respectively. This allows the effect of the present disclosureresulting from the match between the preamble and the SRS transmissionfields to be given to a plurality of SRSs evenly. Moreover, theinfluence of interference resulting from the match between the preambleand the SRS transmission fields can also be distributed evenly over aplurality of SRSs.

Furthermore, when there are a plurality of SRSs in the transmission timefield in which the preamble and the SRS match each other, a transmissionfield that matches that of the preamble may be preferentially assignedto only a specific SRS. For example, as shown in FIG. 11, the SRS havingthe smallest transmission bandwidth (SRS 1 shown in FIG. 11) of aplurality of SRSs (SRS 1 and SRS 2 shown in FIG. 11) may be designatedas a specific SRS. Thus, for an SRS having a small transmissionbandwidth (SRS of a narrowband), it is possible to improve the accuracyof CQI estimation using a preamble as an SRS. For example, SRS 1 may beassigned to a mobile station located at a cell edge, which has a smallsystem bandwidth and which requires improvement of the accuracy of CQIestimation. Here, when a preamble is used as an SRS, the base stationindicates the code sequence to use as the preamble to the mobile stationin advance. This eliminates collision between preambles from differentmobile stations at the base station and allows the base station to usepreambles in the same way as SRSs to be subjected to CQI estimation.

Embodiments of the present disclosure have been explained so far.

As discussed above, a preamble may be associated with an SRS usingequation 1. However, with the present disclosure, it is equally possibleto associate a preamble with an SRS by making m and n in followingequation 1 unequal. For example, the relationship m≦n may be assumedbetween m and n in equation 1. That is, a preamble and SRS may beassociated to constantly satisfy the relationship: preamble transmissiontime interval≧SRS transmission time interval.

Furthermore, the association rules in the embodiments above may bechanged according to the system bandwidth. For example, the 3GPP RAN LTEis studying 1.25/2.5/5/10/15/20 MHz for the system bandwidth. Thus, thepreamble and SRS association rules may be changed for each of theabove-described system bandwidths. This allows the rate at which thepreamble and SRS transmission fields match each other to be set to anoptimum rate for each system bandwidth. Here, the smaller the systembandwidth, the smaller the amount of communication resources available.Therefore, by increasing the rate at which the preamble and SRStransmission time fields match each other as the system bandwidthdecreases, it is possible to provide greater effect of reducing SRScommunication resources.

Furthermore, the embodiments above may adopt a configuration fordetermining whether or not to transmit the SRS in the preambletransmission field according to the cell radius and how often the SRS istransmitted. Especially, applying the present disclosure to only a casewhere the cell radius is small allows transmission and reception withoutinterference between preambles and SRSs. Here, the “cell of a small cellradius” refers to a cell that satisfies following equation 3.Max·RTD≦GT−(CP+SRS)  (Equation 3)

where Max·RTD denotes the maximum RTD of the cell.

Furthermore, the embodiments above may also adopt a configuration inwhich the mobile station determines whether or not to transmit an SRS inthe preamble transmission time field according to the distance betweenthe base station and the mobile station estimated from a path loss levelof a received signal. For example, when the distance between the basestation and the mobile station is small, the mobile station transmits anSRS in the preamble transmission time field. This allows the basestation to prevent interference between the preamble and the SRS. On theother hand, when the distance between the base station and the mobilestation is large, the mobile station does not transmit any SRS in thepreamble transmission time field. This allows the preamble to betransmitted without interference in the preamble transmission timefield. In this case, even if the mobile station does not transmit anySRS, the base station may judge that the channel quality (CQI) is verylow because the distance between the base station and the mobile stationis large. This makes CQI estimation unnecessary, preventing frequencyscheduling using CQI estimate values from being affected.

Furthermore, a case has been described above in the embodiments abovewhere a preamble and an SRS are transmitted from different mobilestations, but when the preamble and the SRS have the same transmissiontime field from one mobile station, the preamble and the SRS may betransmitted simultaneously. For example, the mobile station may arrangean SRS in a guard time of a preamble to be transmitted in the preambletransmission field that matches the SRS transmission field andsimultaneously transmit the preamble and the SRS arranged in the guardtime of the preamble.

Furthermore, in the embodiments above, code sequences may be used whichhave a small cross-correlation between a code sequence used as apreamble and a code sequence used as an SRS. This allows the basestation to reduce interference between the preamble and the SRS causedby a delay of the preamble reception timing.

Furthermore, a case has been described with the present embodiment wherea preamble is transmitted, but similar effects can also be obtained byapplying the present disclosure to a signal with a guard time set in thetransmission time field and transmitted periodically by the mobilestation to the base station.

Furthermore, a case has been described with the present disclosure wherean SRS is transmitted, but similar effects can also be obtained byapplying the present disclosure to signals transmitted periodically fromthe mobile station to the base station.

Moreover, although cases have been described with the embodiments aboveare configured by hardware, the present disclosure may be implemented bysoftware.

Each function block employed in the description of the aforementionedembodiments may typically be implemented as an LSI constituted by anintegrated circuit. These may be individual chips or partially ortotally contained on a single chip. “LSI” is adopted here but this mayalso be referred to as “IC,” “system LSI,” “super LSI” or “ultra LSI”depending on differing extents of integration.

Further, the method of circuit integration is not limited to LSI's, andimplementation using dedicated circuitry or general purpose processorsis also possible. After LSI manufacture, utilization of an FPGA (FieldProgrammable Gate Array) or a reconfigurable processor where connectionsand settings of circuit cells within an LSI can be reconfigured is alsopossible.

Further, if integrated circuit technology comes out to replace LSI's asa result of the advancement of semiconductor technology or a derivativeother technology, it is naturally also possible to carry out functionblock integration using this technology. Application of biotechnology isalso possible.

The disclosure of Japanese Patent Application No. 2007-207187, filed onAug. 8, 2007, including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The present disclosure is applicable to a mobile communication system orthe like.

The invention claimed is:
 1. A communication device, comprising: areceiving unit configured to: receive configuration informationindicating subframes in which Sounding Reference Signals (SRSs) may betransmitted from the communication device; and receive configurationinformation indicating subframes in which random access preambles may betransmitted from another communication device, the random accesspreamble including a cyclic prefix added to a beginning of the randomaccess preamble, the random access preamble being followed by a guardtime, the guard time being a non-transmission period; a mapping unitconfigured to map an SRS to a last portion of a subframe, wherein whenthe random access preamble is transmitted from the other communicationdevice in the subframe, the SRS is temporally aligned with the guardtime; and a transmitting unit configured to transmit the mapped SRS. 2.The communication device according to claim 1 wherein nothing istransmitted by the another communication device in the guard time of thesubframe.
 3. The communication device according to claim 1 wherein therandom access preamble is a preamble sequence selected from a set ofpreamble sequences, and the guard time is of a given time length.
 4. Thecommunication device according to claim 1 wherein when the random accesspreamble is transmitted from the another communication device in thesubframe, the mapping unit is configured to map the SRS in the subframesuch that a time gap between the SRS and the random access preamble ismaximized.
 5. The communication device according to claim 1 wherein whenthe random access preamble is transmitted from the another communicationdevice in the subframe, the mapping unit is configured to map the SRS inthe subframe with a space provided between the random access preambleand the SRS.
 6. The communication device according to claim 1 whereinthe other communication device is non-synchronized in an uplink.
 7. Thecommunication device of claim 1 wherein the received configurationinformation indicating the subframes in which SRSs may be transmittedidentifies a periodicity of subframes in which SRSs may be transmitted,and the received configuration information indicating the subframes inwhich random access preambles may be transmitted identifies aperiodicity of subframes in which random access preambles may betransmitted.
 8. The communication device according to claim 7 whereinthe periodicity of subframes in which SRSs may be transmitted is m/ntimes the periodicity of subframes in which random access preambles maybe transmitted, with m and n being positive integers.
 9. Thecommunication device according to claim 1 wherein at least one of thesubframes in which SRSs may be transmitted is temporally aligned with atleast one of the subframes in which random access preambles may betransmitted.
 10. An integrated circuit, comprising: one or more inputs;and circuitry configured to, in operation: receive configurationinformation indicating subframes in which Sounding Reference Signals(SRS) may be transmitted from a communication device; receiveconfiguration information indicating subframes in which random accesspreambles may be transmitted from another communication device, therandom access preamble including a cyclic prefix added to a beginning ofthe random access preamble, the random access preamble being followed bya guard time, the guard time being a non-transmission period; and map anSRS to a last portion of a subframe, wherein when the random accesspreamble is transmitted from the another communication device in thesubframe, the SRS is temporally aligned with the guard time.
 11. Theintegrated circuit of claim 10 wherein the circuitry is configured to,in operation, output the mapped SRS for transmission.
 12. The integratedcircuit of claim 10 wherein nothing is transmitted by the anothercommunication device in the guard time of the subframe.
 13. Theintegrated circuit of claim 10 wherein the random access preamble is apreamble sequence selected from a set of preamble sequences, and theguard time is of a given time length.
 14. The integrated circuit ofclaim 10 wherein when the random access preamble is transmitted from theanother communication device in the subframe, the SRS is mapped in thesubframe such that a time gap between the SRS and the random accesspreamble is maximized.
 15. The integrated circuit of claim 10 whereinwhen the random access preamble is transmitted from the anothercommunication device in the subframe, the SRS is mapped with a spaceprovided between the random access preamble and the SRS in the subframe.16. The integrated circuit of claim 10 wherein the another communicationdevice is non-synchronized in an uplink.
 17. The integrated circuit ofclaim 10 wherein the received configuration information indicating thesubframes in which SRSs may be transmitted identifies a periodicity ofsubframes in which SRSs may be transmitted, and the receivedconfiguration information indicating the subframes in which randomaccess preambles may be transmitted identifies a periodicity ofsubframes in which random access preambles may be transmitted.
 18. Theintegrated circuit of claim 10 wherein the configuration informationindicating the subframes in which SRSs may be transmitted identifies aperiodicity of subframes in which SRSs may be transmitted, and theconfiguration information indicating the subframes in which randomaccess preambles may be transmitted identifies a periodicity ofsubframes in which random access preambles may be transmitted, whereinthe periodicity of subframes in which SRSs may be transmitted is m/ntimes the periodicity of subframes in which preambles may betransmitted, with m and n being positive integers.
 19. The integratedcircuit of claim 10 wherein at least one of subframes in which SRSs maybe transmitted is temporally aligned with at least one of subframes inwhich random access preambles may be transmitted.